The main purpose of the Transgenic Core is to provide a service facility that will ensure the ability of each DERC member to produce transgenic and chimeric mice from embryonic stem cells as well as transgenic rats. We will provide transgenic and knockout mice in the NOD system as our primary service. We will also provide transgenic mice in F2 (usually B6/C3H) and rats on Sprague-Dawley, and chimeric mice using the 129 strain ES cells. Embryo freezing will be provided as a means to preserve valuable, but not used, strains of mice. We will also establish an in vitro fetrilization procedure which will allow the cryopreservation of sperm in addition to embryos. In addition, the Core will develop a new immunodeficient rat model to be used as a system for studying human tissue grafts, BAC (bacterial artificial chromosomes) transgenic NOD mice to define specific diabetes susceptibility genes, and use NOD/129 F1 ES cells for NOD knockout and knockin experiments. The goal of the Transgenic Core is to provide DERC members and their collaborators with unique rodent models that are not easily duplicated by commercial facilities.